Art of working metals



Patented Oct. 16, 1934 UNITED. STATES 1 59 NT OFFICE PATE ART or woaxmc METALS Herbert R. Treating, Newark, N. .L, alsignor to American Machine at Foundry CompanyyNew York, N. Y., a corporation of New Jersey I No Drawing. Application January 5, 1934, Serial No. 705.346

10 Claims.

This invention relates to the art of workingmetal or alloys. and is applicable to the working of most of the special steels going into the manufacture of a large number of commercial products. Some of the blanks treated in accordance with the principles of the present invention result in products of-unusual construction and composition and exhibit characteristics which make them peculiarly adapted for the uses towhich they are to be put.

The process of the invention involves the use of a coating of lead or lead composition as a lubricant for working the metal blank which is to be rolled, stamped, drawn or otherwise deformed. This lubricant differs from previously known lead-containing material designed for this purposebecause of its peculiar composition and its ability tenaciously to adhere to the metal to which it is applied. This facilitates the mechanical work to be done upon the metal blank by ensuring the presence of the lubricant at the point or points of greatest stress at times when such blank is forced or drawn into or through the die, draw plate, mandrel, ring, roller or other metal-working instrumentality used for accomplishing the desired purpose. Friction is reduced and the stresses and'strains which cause crystallization of the metal are minimized to an extent which reduces the number of annealings, and in some cases entirely dispenses with the necessity of annealings usually necessary between successive working operations. The lubricant is very easily removed during a final annealing treatment by melting or volatilizing the lead-containing lubricating material, or by decomposing the same and melting or volatilizing the products of decomposition. When coated products are required, this final annealing may be followed by an added dipping in the molten lubricant, which in such case hardens on the blank and servesas an excellent protection against corrosion and deterioration.

Lead has heretofore been suggested for lubricating-metaleworking operations but the methods used to accomplish the desired result have been unsatisfactory because of the diflicultyof bonding the lead firmly to the metal blank, and because of the difliculty of removing the lubricant when it is desired to do so after the metal blank has been worked. In connection with the first of these difficulties it has been suggested than an amalgam formed in the surface of the metal blank will facilitate working by itself or will enable a coating of lead to be applied by dippin in a molten bath, which coating of lead also facilitates.

the working of the blank. This procedure is said to reduce the number of intermediate annealings necessary in drawing steelwires and tubes, but the process is otherwise complicated by the steps required to produce the amalgam, so that very little saving in time and labor is actually obtained. Moreover, the use of an amalgam accentuates the second difficulty, i. e., the proper removal of the lubricant from the surface of the blank. Accordingly, it has been found very difficult to remove lead coatings applied through the use of an amalgam and resort must be had to the use of special pickling or tie-leading solutions which are not only likely to injure the surface of the worked blank but result in an increase in the time, labor and consequently the expense of the process.

I have found that lead may be made to adhere very satisfactorily to metal blanks by dipping the metal in a molten bath containing lead and phosphorus, the phosphorus being to the extent of 25% or less. A small quantity of tin may be added to the lead bath preparatory to incorporating the phosphorus, andin such case a percentage of phosphorus as low as or less than .0008% has been found highly emcient in promotingadhesion. More phosphorus may be incorporated by increasing the amount of tin in the composition.

'The phosphorus is preferably incorporated by immersing a semi-closed container or capsule containing red phosphorus in the molten bath as described and claimed in the application of Daniel D. Jackson, Serial No. 609,008, filed May 3, 1932. This is a very effective way of incorporating phosphorus in the bath, and the presence of such phosphorus insures the formation of a tenacious bond between the lead material and the metal blank desired to be worked.

The lead lubricating material applied as above indicated is to some extent removed during the last working operation, but may be completely eliminated during a subsequent annealing operation carried out at a temperature which melts or volatilizes it or decomposes it into its constituent the pores of the metal workpiece.

Exemplary of the process of the invention is the working of a wire by drawing, for instance, drawing a .050" stainless steel wire containing iron, chromium and nickel. Such a wire is ordinarily very di'flicult to work as it becomes quickly crystallized or work-hardened during working,

thus rendering it brittle and subject to corrosion. The wire is passed through a molten bath containing, for example, about 97 /2% lead, 2 /z% tin, and a very small percentage of phosphorus. The wire is then led through appropriate dies and drawn to successively smaller diameters. Due to 5 the excellent lubricating qualities, the wire may be drawn twenty or more times without workhardening of the wire, that is, without crystallization of the structure of the metal to an extent requiring a crystal rearrangement by annealing. When annealing is required or desired, it is accomplished by running the wire through a suitable furnace where it is "strand annealed at about 1900-1950 F. although it may be coil annealed, i. e., annealed in coil form. The wire may then be cleaned by pickling, dipped in the lead bath and then led through another series of dies and brought down to a smaller diameter and subsequently annealed again. This procedure is repeated until the wire is of, or approximately of, the desired diameter, the last annealing serving substantially completely to de-lead the wire and to cause whatever lead material remains on the surface or in the surface pores to bleed out of the wire and to be melted or volaof the materials of the lubricant has taken place, such as the formation of lead oxide, the heat of annealing causes the compound to bleed out and then to decompose into, its constituent elements which are melted or volatilized and thus freed from the wire. This is due to the fact that the temperature of annealing iskept at a point above the melting or volatilization points of the constituents of the lubricant and. above the points at. which they remain combined as stable compounds. Any residue remaining on the wire after the last annealing may be scraped off by a final drawing designed to bring the wire down to the exact size desired.

I have found that the above described .050 wire may be drawn down to a clean .009 wire in twenty passes or draws, without any intermediate annealings, thus enabling the finished wire to be obtained with great facility and economy. This contrasts sharply with ,the ordinary method of drawing such a wire which requires an annealing after every few draws. It will be seen that the present process retards work-hardening to an extent which permits a large reduction in the phosphorus in any case, a quarter of one percent. being more than ample for the purposes desired,

and as previously indicated, as little as .0008% being quite satisfactory. Substitution of a small .amount of bismuth for a proportion of the lead and tin, is advantageous for the purpose of inif creasing the plasticity of the lubricant and rer ducing the degree of temperature necessary to bring it to molten condition, and in such case it is desirable to use a higher percentage of phosphorus than would otherwise be required.

tilized; or, in the event a chemical combination number of annealings, and as a new pickling or dipping is required after each annealing, a corre-.

and .3%-10% tin, with a very small amount of The annealing treatment is preferably carried out in a furnace open to the atmosphere but may, if desired, be carried out in a hydrogen or other non-oxidizing atmosphere.

The lubricant tenaciouslyadheres to the metal blank (the wire in the specific illustration) and appears to ball" around the die or other working member, thus masking its effect and eliminating scratching of the blank by the sharp edges of the die or by grit. The metal is smooth after passage through the die and is free from scratches and scores.

In the event a de-leaded product is not desired, as is the case where a protective lead coating is desired on the finished article, the final annealing may be omitted, or the final annealing may be followed by a final dipping. Thus, in the case of a brass, copper or bronze wire designed for use in a storage battery cable, the lead material is left on' the wire and forms a very effective corrosion and deterioration resistant coating.

While the invention has been illustrated specifically in connection with drawing wire, it should be understood that it is equally applicable to stamping, rolling or otherwise working metal blanks which may be produced in soft annealed state or in a relatively hard or non-annealed condition, either with or without a protective coating of lead material.

What I claim is:

l. The process of working metal blanks comprising coating a blank with lead containing phosphorus and then working said blank into the desired form.

2. The process of working metal blanks comprising coating a blank with a lead-tin alloy containing' phosphorus and then working said blank into the desired form. I

3. The process of working metal blanks comprising coating a blank with lead containing pho'sphorus, working said blank into the desired form and then removing residually adhering lead material by subjecting the blank to heat.

- 4. The process of treating metal .blanks comprising working the same while lubricating the points in contact with the working instrumentality with lead containing phosphorus. I

5. The process of treating metal blanks comprising working the same while lubricating the points in contact with the working instrumentality with lead containing phosphorus, and removing rasidually adhering lead material by subjecting the blanks to heat.

6. The process of treating metalblanks comprising working the same while lubricating the points in contact with the working instrumentality with lead containing tin and phosphorus.

.7. The process of treating metal blanks comprising working the same while lubricating the points in contact with the working instrumentality with lead containing tin, bismuth and phosphorus.

8. The process of drawing wire comprising coating the workpiece from which the wire is to be drawn with lead containing phosphorous, and then drawing the work-piece.

9. A lubricant for metal working comprising lead containing phosphorus.

10. A lubricant for metal working comprising lead containing tin and phosphorus.

' HERBERT R. TREUTING. 

